Method of manufacturing contoured consolidated cellulosic panels with variable basis weight

ABSTRACT

A method of manufacturing a contoured, consolidated cellulosic article, with variable basis weight, is disclosed. The method employs a former to create a mat having a substantially uniform thickness which is pre-pressed to retain its shape. The pre-pressed mat is then machined along at least one surface to result in a desirable contour. The contoured mat is then consolidated within a secondary press. The secondary press preferably includes platens shaped complimentarily to the surfaces of the mat.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to wood products and, more particularly,relates to methods of manufacturing consolidated cellulosic panels.

2. Description of Related Technology

Consolidated cellulosic panels, such as fiber board, paper board,particle board, and the like, are typically comprised of wood furnishsuch as saw dust, shavings, chips, or specially ground fibers,compressed with a binding agent or resin under heat and pressure. Suchboards can be used in a variety of applications including, but notlimited to, exterior house siding, interior and exterior door facingpanels or door skins, cabinet doors, paneling, moulding, etc.

It is often desirable to manufacture such panels to a uniform basisweight and caliper. If the panels are flat this can be accomplished bycompressing a mat between first and second flat faced dies. However, ifone of the faces needs to be deeply contoured, such die compressionshave proven to be problematic. For example, if a first die has a contourcorresponding to the desired shape of the panel, and the second die hasa flat face, the mat compressed therebetween will have a non-uniformcaliper, with the thinner areas of the mat being compressed to a higherdensity than thicker areas. This is especially true with fiberousmaterials that do not flow under pressure.

Current methods of producing such panels therefore typically requirethat a mat having first and second opposed flat surfaces be compressedaccording to conventional methods, and that one or more of the surfacesthen be machined to have the desired contour. For example, a router maybe used to shape the surfaces. U.S. Pat. No. 4,175,106, assigned to thepresent assignee, discloses such a process. Such tools, however, cannoteasily produce sharp inside corners, are relatively slow, and requirecomplex, expensive equipment.

Another method requires contoured, complementary, dies on both the topand bottom to produce a substantially uniform thickness through thecontoured and non-contoured areas. If one of the top or bottom needs tobe flat, or alternatively shaped, the panel must undergo an addedmachining step adding time, expense and waste to the operation. Shallowcontouring of one face is typically done in an embossing operation, orwith an embossing die, but the depth of embossing is greatly limited.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, a method ofmanufacturing a contoured, consolidated cellulosic article having avariable basis weight is provided. The method comprises the steps offorming a loose mat of cellulosic material and a binder resin, the mathaving a top surface and a bottom surface, machining at least one of thetop surface and bottom surfaces to have a pattern, and consolidating themat between a top platen and a bottom platen. The top and bottom platenshave contours complementary to the patterns machined into the mat topand bottom surfaces, respectively.

In accordance with another aspect of the invention, a method ofmanufacturing a consolidated cellulosic article is provided comprisingthe steps of depositing cellulosic fiber and a binding agent onto amoving conveyor to form a mat, applying suction through the conveyorbelt, scalping a top surface of the mat, compressing the mat betweenupper and lower platens at a first pressure, machining a pattern intothe top surface by removing cellulosic material in a desired pattern,gathering the removed cellulosic material, and compressing the matbetween third and fourth platens. The conveyor is perforated so as toenable the suction to hold the mat onto the belt. The scalping stepcreates a mat of uniform height. The third and fourth platens arecontoured complimentarily to contours of the top and bottom surfaces,respectively.

In accordance with another aspect of the invention, a method ofmanufacturing a contoured, consolidated cellulosic article with variablebasis weight is provided, which comprises the steps of forming a loosemat of cellulosic material and a binder resin, the mat having a topsurface and a bottom surface, prepressing the loose mat to a firstdensity and caliper, machining at least one of the top surface andbottom surface to have a pattern, and consolidating the mat between atop platen and a bottom platen. The top and bottom platens have contourscomplementary to the pattern machined into the mat top and bottomsurface, respectively. The consolidating step compresses the mat to asecond density and caliper. The second density is greater than the firstdensity.

These and other aspects and features of the invention will become moreapparent upon reading the following detailed description when taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of an article constructed in accordance withthe teachings of the invention;

FIG. 2 is a schematic representation of a mat being preliminarily formedaccording to the teachings of the invention;

FIG. 3 is a partial sectional view of a mat being pre-pressed accordingto the teachings of the invention;

FIG. 4 is a schematic representation of a mat being machined in twodimensions according to the teachings of the invention;

FIG. 5 is a schematic representation of a mat being machined in threedimensions according to the teachings of the invention;

FIG. 6 is a partial sectional view of a mat being compressed under heatand pressure according to the teachings of the invention; and

FIG. 7 is a schematic representation of a system constructed inaccordance with the teachings of the invention.

While the invention is susceptible to various modifications andalternative constructions, certain illustrative embodiments thereof havebeen shown in the drawings and will be described below in detail. Itshould be understood, however, that there is no intention to limit theinvention to the specific forms disclosed, but on the contrary, theintention is to cover all modifications, alternative constructions, andequivalents falling within the spirit and scope of the invention asdefined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, and with specific reference to FIG. 1, anarticle constructed in accordance with the teachings of the invention isgenerally referred to by reference numeral 20. While the article 20 isdepicted as a six panel door facing, it is to be understood that theteachings of the invention can be employed in the construction of anynumber of other consolidated cellulosic articles having a contouredsurfaces such as, but not limited to, exterior house siding, interiorand exterior door facing panels or door skins, cabinet doors, paneling,and moulding.

As shown in FIG. 1, the article 20 includes a first or top surface 22, asecond or bottom surface 24, first and second side edges 26, 28, andfirst and second end edges 30, 32. The top surface 22 is contoured,whereas the bottom surface 24 is flat or planar in the depictedembodiment. More specifically, the top surface 22 includes a pluralityof indentations 34 of various dimension and depth to provide anappearance desirable for the end application of the article 20. In thedepicted embodiment, the bottom surface 24 is flat to facilitateattachment of the article 20 to a door core, but it is to be understoodthat the article 20 may include a back surface having a non-flat contouras well.

Referring now to FIG. 2, a former 36 according to the teachings of theinvention is depicted generating a mat 38. The former 36 includes ahopper 40 from which a combination of cellulosic fibers and a bindingagent or resin are deposited onto a moving conveyor belt 42. The bindingagent may be any number of different known agents including, but notlimited to, phenolic resin or isocyanate. The conveyor belt 42 ispreferably perforated, with a suction device 44 being proximate theconveyor belt 42. The suction device 44 generates a pressuredifferential across the conveyor belt 42 thereby holding the mat 38 tothe conveyor belt 42.

As can be seen in FIG. 2, the cellulosic material is deposited upon theconveyor belt 42 at an inconsistent height (exaggerated in FIG. 2 forthe purpose of illustration). Accordingly, downstream of the hopper 40 arotary scalper 46 may be provided. The scalper 46 includes a rotatingaxle 48 from which a plurality of blades 50 radially extend. Rotation ofthe scalper 46 causes the blades 50 to engage the mat 38 and therebyreduce the mat 38 to a consistent thickness. It is to be understood thatthe scalper 46 may be provided in alternative forms, such as saw blades,for removal of the cellulosic material.

Referring now to FIG. 3, a pre-press 52 according to the teachings ofthe invention is depicted. The pre-press 52 includes a first platen 54as well as a second platen 56 which are adapted to be compressedtogether as by hydraulic cylinders 58. The pre-press 52 compresses themat 38 to a softboard 53, defined herein as a compressed mat ofcellulosic fiber and a binding agent having a relatively low density,e.g., 10 to 30 lbs. per cubic foot. Such a softboard has sufficientdensity and strength to maintain its shape, as opposed to being a loosepile of fibers, but would not be suitable for use as a solid productsuch as siding or doors. The softboard 53 is preferably formed in theabsence of heat or moisture so as to avoid curing of the binding agentand thereby allow for the material removed, as by the rotary scalper 46,to be recycled.

Once the softboard 53 is formed, it is machined as shown in FIGS. 4 and5, resulting in a softboard 53 having a variable basis weight across itsdimension. For example, as shown in FIG. 4, the top surface 22 of thesoftboard 53 may be machined along a single axis, e.g., a longitudinalaxis a, to provide a contoured top surface 22 while maintaining thebottom surface 24 in a planar configuration. If the softboard 53 ismachined as depicted in FIG. 4, wherein a second rotary scalper 60removes material along the longitudinal axis ∝, (as well as a depth axisΔ) material such as house siding can be easily manufactured. If the endproduct needs to be machined along the longitudinal and lateral axes αand β (as well as along the depth axis Δ) as with a six panel door asdepicted in FIG. 1, a router 62 may be employed as shown in FIG. 5. Therouter 62 is preferably mounted on a track system 64 and connected to aCNC control (Computer Numerical Control) or the like for movement of therouter 62 in appropriate directions.

Referring now to FIG. 6, a secondary press 68 according to the teachingsof the invention is shown in partial sectional view. The secondary press68 preferably includes an upper platen 70, a lower platen 72 and amechanism for compressing the upper and lower platens 70 and 72together. Such a mechanism may be provided in the form of hydrauliccylinders 74, but may be provided in any other type of actuatorincluding, but not limited to, pneumatic cylinders, motors, and thelike.

In the depicted embodiment, the upper platen 70 includes a plurality ofprotrusions 76 such that the contour of the upper platen 70 iscomplimentarily shaped to a pattern 78 form in the upper or top surface22 of the softboard 53. Also in the depicted embodiment, the lowerplaten 72 is flat or planar so as to match the planar shape of thebottom surface 24, but it is to be understood that if the bottom surface24 is otherwise contoured, the lower platen 72 would be shaped tocorrespond to the contour of the bottom surface 24.

The secondary press 68 preferably has a heat source 75 associatedtherewith to compress the softboard 53 under heat and pressure. The heatsource 75 may be provided in the form of heat exchanger coils orchannels through the platens 70, 72, through which heated fluid, e.g.,water, is circulated, or in the form of separate hot platens.

Referring now to FIG. 7, a system 80 according to the teachings of theinvention is shown in schematic fashion. As shown therein, the system 80includes the former 36, the pre-press 52, a machining mechanism 82, thesecondary press 68, as well as a gathering mechanism 84 and a recyclingmechanism 86.

The machining mechanism 82 may be provided in the form of theaforementioned rotary scalper 60 or router 62, but can alternatively beprovided in the form of any other type of mechanism for removingcellulosic material from the mat 38 including, but not limited to,circular saw blades, band saw blades, sanders, and the like. Thegathering mechanism 84 may be provided in the form of a conveyorprovided below the machining mechanism 82, or may be provided in theform of a vacuum device for drawing the removed cellulosic materialaway. The recycling mechanism 86 preferably communicates the materialgathered by mechanism 84 back to the former 36 for use in the formationof subsequent articles 20. Accordingly, the recycling mechanism 86 mayinclude conveyors, suction lines, or the like.

From the foregoing, it will be appreciated that the teachings of theinvention may be employed to manufacture a contoured, consolidatedcellulosic article having variable basis weight.

1. A method of manufacturing a contoured, consolidated cellulosicarticle, having a variable basis weight, comprising the steps of:forming a loose mat of cellulosic material and a binder resin; trimmingthe mat to a preslected height by scalping the upper portion of the matwith a first rotary scalper; creating a softboard by pre-pressing themat at a first pressure between first and second platens, the softboardhaving a top and a bottom surface and being formed in the absence ofheat to avoid curing of the binder resin; machining at least one of thetop and bottom surfaces to have a pattern; and consolidating the matbetween a third platen and a fourth platen at a second pressure that isgreater than the first pressure, the third and fourth platens havingcontours complementary to contours in the mat top surface and bottomsurface, respectively.
 2. The method of claim 1, wherein the formingstep is performed by sprinkling cellulosic fiber and a binder resin ontoa moving conveyor belt.
 3. The method of claim 2, further including thestep of applying suction through the conveyor belt to hold the mat tothe belt and ensure that the mat is trimmed to a pre-selected height,the suction is applied during the forming step and prior to the trimmingstep.
 4. The method of claim 1, wherein the softboard has a densitywithin the range of about 10 to about 30 pounds per cubic foot.
 5. Themethod of claim 1 wherein the machining step is performed along one of alongitudinal and lateral axis of the mat.
 6. The method of claim 1 ,wherein the machining step is performed along both a longitudinal andlateral axis of the mat.
 7. The method of claim 5, wherein the machiningstep is performed using a second rotary scalper.
 8. The method of claim6, wherein the machining step is performed using a computer numericallycontrolled router.
 9. The method of claim 1, wherein the consolidatingstep is performed under heat and pressure.
 10. The method of claim 1,further including the steps of gathering the cellulosic material duringthe machining step, and reusing the gathered cellulosic material insubsequent iterations of the forming step.
 11. A method of manufacturinga consolidated cellulosic article, comprising the steps of: depositingcellulosic fiber and a binding agent onto a moving conveyor belt to forma mat, the conveyor belt being perforated; applying suction through theconveyor belt, the applied suction holding the mat to the belt; scalpinga top surface of the mat, the scalping step creating a mat of uniformheight; pressing the mat between upper and lower platens at a firstpressure to form a softboard, the softboard being formed in the absenceof heat to avoid curing of the binder resin; machining a pattern intothe top surface by removing cellulosic material in a desired pattern;gathering the removed cellulosic material; and compressing the matbetween third and fourth platens, the third and fourth platens havingcontours complementary to a top and bottom surface of the mat,respectively.
 12. The method of claim 11, wherein after the pressingstep the mat has a density within the range of about 10 to about 30pounds per cubic foot.
 13. The method of claim 11, wherein the machiningstep is performed along one of a longitudinal and lateral axis of themat.
 14. The method of claim 13, wherein the scalping step is performedby a first rotary scalper and the machining step is performed using asecond rotary scalper.
 15. The method of claim 11, wherein the machiningstep is performed along both a longitudinal and a lateral axis of themat.
 16. The method of claim 15, wherein the machining step is performedusing a computer numerically controlled router.
 17. The method of claim11, wherein the compressing step is performed using a computernumerically controlled router.
 18. The method of claim 11, furtherincluding the step of reusing the removed cellulosic material insubsequent iterations of the depositing step.
 19. A method ofmanufacturing a compressed cellulosic product having a three dimensionalsurface and a variable weight basis, the method comprising: depositingunconsolidated cellulosic material and a binder resin on a movingconveyor belt, the conveyor bolt being connected to a suction device sothat the unconsolidated cellulosic material and binder resin aresecurely affixed to the conveyor belt and thereby form mat on thesurface of the conveyor belt; scalping the upper portion of the mat witha first rotary scalper so that the mat has a uniform preselectedcaliper; pressing the mat between first and second platens at a pressuresufficient to form a softboard having a density between 10 and 30 poundsper cubic feet, the softboard being formed in the absence of heat toavoid curing of the binder resin; machining the softboard with a secondrotary scalper to contour the surface of the softboard and therebyestablish a variable weight basis; pressing the softboard between thirdand fourth platens in a presence of heat and a pressure, the pressurebeing greater than the first mentioned pressure, the third and fourthplatens having contours corresponding to the machined surface of thesoftboard, and thereby forming a cellulosic product having a densitygreater than the density of the softboard.